Telephone system



Jan. 1, 1929.

B. D. WILLIS TELEPHONE SYSTEM HAITI/Y5 AND REvEKr/m; CALL TONE.

InuE u1"- Patented Jan. 1, 1929.

UNITED STATES PATENT OFFICE.

BERNARD D. WILLIS, 0F OAK PARK, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- WARE.

( TELEPHONE SYSTEM.

Application filed April 23, 1924. Serial No. 708,381.

This invention relates to telephone systems in general, but more particularly to so-called call. distributing or traffic distributing systems in which manual switchboards are used and automatic switches are employed for distributing the calls to the operators.

Generally stated, the object of the invention is to provide an improved and highly etiicient telephone exchange system of the foregoing character.

Special objects of the invention are the provision of a cut-in control switch whereby waiting calls are cut in to the operator in successive order; the provision of a waiting tone placed on the calling subscribcrs circuit to notify him when his call has been cut in to the operator, whereupon he orders his connect-ion without waiting for the customary number please; the'provision of a plug ending cord circuit whereby the operator plugs into the multiple jack of the desired station without making a busy test and said circuit distinguishes between a busy line, a free line, or a line where a. subscriber is calling the party on the same line, and then automatically disconnects the operator and connects the busy signal or ringing current, or holds the operator and notifies her with a characteristic tone, as the case may require; and the provision of a single supervisory lamp associated with a cord circuit and suitable circuit arrangements whereby intermittent fiashes notify the operator of a call and designate the cord selected, and an unlighted or lighted condition gives connect or disconnect supervision in the usual well known manner.

7 To accomplish the foregoing and other useful ends this invention comprises means which will be fully described in the specification which is to follow, reference being bad to the accompanying drawing, which shows diagrammatically the apparatus and circuits involved in a system embodying the invention;

The substations A and A are connected in bridge of a single pair of talking conductors and are arranged for selective ringing to ground. As represented herein, substation A comprises essentially the receiver 2, switchhook 3, transmitter 4, condenser 5, and hell 6.

The line conductors 11 and 12 of the substations A and A terminate at the central ofiice in the individual line switch G and multiple jacks such as J and J, there being a ack for each station at each switchboard section. These jacks are so wired at a distributing frame that the stations will be rung lndlvldually to ground over different sides of the line by merely inserting the cord plug 1n the usual well known manner.

The line switch C is mechanically of the rotary type in which the wipers have no normalposition and move in a forward direct-ion only. It has access to a plurality of trunk lines extending to cord circuits at a plurality of operators positions.

The cord circuit TD consists essentially of a plurality of relays and condensers, a plug P, and a signal lamp L, together with associated common ringing, busy tone, Waitmg and reverting call tone, and interrupted ground equipment, and suitable circuits for Iperforming the necessary functions, as will e pointed out hereinafter.

Associated with the cord circuit TD and the other cord circuits at the same position is a common finder and cut-in control switch S, conslsting of a plurality of relays, a double ended wiper, and a stepping magnet that rotates the wiper in a forward direction only (having no normal position) over a plurality of contacts each of which corresponds to a diiferent cord circuit. An 'operators well known head set circuit is shown diagram matically at 0 together with an emergency step key K for operating the switch S.

The substations A and A are similar to A and A, and at the central office the line conductors across which they are bridged terminate in the individual line switch C, which is similar to the line switch C, and station multiple jacks J 2 and J which are similar to the jacks J and J.

Having briefly explained the purpose of the invention and the apparatus involved in carrying it out, the operation of the equipment may now be explained more in detail. For this purpose it will be assumed that the subscriber at substation A desires to obtain connection with the subscriber at substation A. In order to do this, the subscriber at substation A removes his receiver and when he is cut in to the operator he gives her the numductors 11 and 12. Upon energizing, line cuit for switching relay 13 and stepping magnet 15 in series. As a further result of the energization of line relay 14, it connects test wiper 22 to the junction of switching relay 13 and stepping magnet 15 at armature 20.

In case the trunk upon which the wipers of the line switch are standing is idle, switching relay 13 energizes immediately. Assuming the trunk to be busy, however, switching re ay 13 is short circuited by ground encountered on the busy test contact by test wiper 22 and does not energize, and the wipers are rotated step by step by the buzzerlike action of stepping magnet 15, which operates through the test Wiper 22. When an idle trunk is reached, which trunk it will be assumed is the one terminating in bank contacts 24, 25 and 26, switching relay 13, being no longer short circuited, energizes in series with stepping magnet 15. Stepping magnet 15, however, does not energize at this time on account of the high resistance of switching relay 13. Switching relay 13, upon energizing, opens a point in the test circuit and prepares the holding circuit at armature 17, and at armatures 16 and 18 disconnects line conductors 11 and 12 from the winding of line relay 14 and ground, and extends them by way of Wipers 21 and 23, and bank contacts 24 and 26 to the upper and lower windings of line relay 42 of the cord circuit TD.

When the line switch C selects the idle cord circuit TD a waiting tone is placed on the calling subscribers line circuit which will persist until his call is cut in to the operator as will be more fully explained hereinafter. This waiting tone circuit may be traced from the tone apparatus indicated, resting con tact of armature 81 and said armature, resting contact of armature 65 and said armature, lower heavy talking conductor and talking condenser, bank contact 26, wiper 23, working contact and armature 18, line conductor 11, over the calling subscribers loop to line conductor 12, armature 16 and its working contact, wiper 21, bank contact 24, to a point where it divides; one branch extending by way of normally closed contacts controlled by armature 53, and through theupper winding of relay 42 to grounded battery, while the other branch extends by way of the upper talking condenser and through theupper winding of relay 41 to grounded battery.

Line relay 42 of the cord circuit TD energizes over the calling subscribers loop and at armature 56 closes a circuit for relay 40, and at armature 57 closes a circuit for relay 44 by way of ground at armature 80. Relay 40, upon energizing, closes at armature 55 a circuit for relay 43, and at armature 39 places ground on the release trunk conductor, thereby closing the usual holding circuit for switching relay 13 of the line switch C before the slow' acting relay 14 has had time to deenergize. Relay 43 energizes and further opens at armatures 58 and 59 circuits to be explained hereinafter. Relay 44, upon energizing, closes a circuit at armature 61 for relay 103 of cordfinder and cut-in control switch S, and at armature 60 disconnects the test wire 100 from ground and connects it to relay 45.

When relay 103 of the cut-in control switch energizes, a circuit is closed at armature 110 for relay 101 by way of armature 108 and its resting contact. Relay 101, upon energizing, closes a circuit at armature 106 for relay 102 by way of armature 112 and stepping magnet 104; and closes a circuit at 'armature 105 which may be traced from grounded conductor 113, leading from one of the plurality of cord circuits other than TD, wiper 111, working contact of armature 109 and said armature, armature 107 and its resting contact, armature 105 and its working contact, and resting contact of armature 112 and said armature to grounded battery at stepping magnet 104. Relay 102 will not energize in series with the stepping magnet due to being shunted out by the latter traced circuit. Stepping magnet 104, upon energizlng and deenergizing, rotates the wiper 111 into contact with the next conductor leading from a cord circuit and if such conductor is unseized, or grounded, it will operate again and will continue to rotate the wiper by its buzzer-like action until an ungrounded bank contact is found such as the bank contact of the conductor 100 of the seized cord circuit TD. 'VVhen this contact is reached magnet 104 is prevented from energizing again, while relay 102, upon energizing, opens at armature 108 the circuit of relay 101, and closes at armature 107 an energizing circuit for relay 45 which may be traced from ground, working contact of armature 106 and said armature, working contact of armature 107 and said armature, armature 109 and its working contact, wiper 111, conductor 100, armature 60 and its working contact to grounded battery at relay 45. Relay 101, being slow acting. holds up sufiiciently long to permit relay 45 to energize.

Relay 45 of the (.()1'(l circuit TD, upon energizing, closes a locking circuit for itself and relay 102 at armature 64 which extends from ground, armature 80 and its resting contact, armature 64 and its working contact, working contact of armature 60 and said armature, conductor 100, wiper 111, working contact of armature 109 and said armature, armature 107 and its working contact, relay 102, resting contact of armature 112 and said armature, and magnet 104 to grounded battery. In addition, relay 45'opens at armature 65 the circuit of the waiting tone; closes at armatures 62 and 65 a circuit to the operators head set 0, which circuit includes the calling subsc'ribers loop and closes at armature 63 a circuit including the ground interrupter I and supervisory lamp L, whereby the lamp is flashed to notify the operator of the call and designate the cord selected. When the waiting tone isdisconnected the calling subscriber knows he is connected with an operator and without waiting for the customary number please he orders the desired connection, in this case with the subscriber at station A The operator may nowpick up the plug P associated with the flashing lamp L and insert it into the multiple jack J of the desired station A without making the usual busy test. If the line is not busy a circuit may be traced from ground, resting contact of armature 218 and said armature, ring conductors of multiple jack J 2 and plug P, armature 79 and its resting contact, working contact'of armature 38 and said armature, relay 49, resting contact of armature 78 and said armature, tip conductors of plug P and multiple jack J armature 216 and its resting contact, and relay 214 to grounded battery. Relay 214 will not energize in series with relay 49 due to the high resistance of the latter. Relay 49, upon energizing, closes a circuit at armature 76 as follows: Ground, relay 51, working contact of armature 7 6 and said armature, normally closed contact controlled by armature 84, sleeve conductors of plug P and multiple jack J relay 213, magnet 215, and grounded battery. This circuit busies the called line, at the multiple acks, to other incoming calls. Relay 213 now energizes but due to the usual mechanical interlocking device between the armature of the relay 213 and the armature of relay 214, the former is energized only half way and as a result the wipers of the called line switch are not connected up, although relay 214 and ground are disconnected from the called line at armatures 216 and 218. As a further result of the energization of relay 49, a circuit is closed at armature 87 for relay 95 by way of ground at armature 72; but due to this relay being slow to energize it will not actuate its armature before its circuit is again opened at armature 87 by the deenergization of-relay 49, which occurs when ground is disconnected fron'i arn'iaturc 218;

In the cord circuit TD, relay 51 energizes in series with relay 213 and at armature 84 closes a locking circuit for itself, which includes the resistance 93 in parallel to lower the ground potential on the sleeve conductor; at armature 85 closes a circuit for relay 50; and at armature 82 closes the ringing circuit. Relay 50. upon energizing, prepares at armature 77 a disconnect signal circuit for lamp L; re-

moves at arinatures 7 8 and 79 the relay 49' from across the talking conductors; further a 7 opens at armature 81 the waiting tone circuit; opens at armature 80 the circuits of relays 44, 45 and 102, and prepares a locking circuit for relay 46. Relay 45, upon deenergizing, disconnects at armatures 62 and 65 the operators head set 0 and disconnects at armature 63, interrupted ground I which extinguishes the flashing supervisory lamp L, thus indicating to the operator that the connection is'proceeding regularly. Relay 102, upon deenergizing, opens at armature 107 its locking circuit; and prepares at armature 108 a circuit for relay 101. Relay 44, being slightly slow to release, holds up just long enough to insure the deenergization of relay 102, as mentioned above, and upon deenergizing, replaces battery with ground potential on conductor 100 at armature 60; and opens at armature 61 the circuit of relay 103. If there are no calls stored up relay 103 will deenei'gize and switch S will rest until an associated cord circuit is seized when it will again operate as above. If calls are stored up in an operators position, havinga plurality of cord circuits, and the common equipment shown, relay 103 will not denergize, due to ground potential being present at each seized cord circuit (at an armature similar to 61), but will cause the switch S to hunt for the other seized cord circuits taking them in order one at a time as the switch rotates.

As referred to above a ringing circuit'is closed when relay51 energizes. The ringing circuit may be traced from the grounded bell at the called substation A line conductor 211, tip conductor of the jack J 2 and plug P, work ing contact of armature 82 and said armature, armature 66 and its resting contact, upper winding of relay 46, armature 90 and its working contact, to the usual well known generator, as indicated. Relay 46 being marginal will not operate in serieswith the ringer and condenser at the called substation. The ringing of thecalled subscribers bell continues intermittently until he answers by removing his receiver from the switchhook, or until the operator pulls down the connection, the calling subscriber receiving the usual well known ringing tone by way of armature 83 and its working contact, as long as the ringing continues and he holds the receiver to his ear.

When the called subscriber answers a direct current bridge is closed across the conductors of the line, thereby operating relay 46 in the cord circuit TD. This circuit may be traced from ground, resting contact of armature 68 and said armaturefarmature 86 and its working contact, ring conductors of I plug P and jack J line conductor 212, transmitter and receiver at the substation A line conductor 211, tip conductors of the jack J 2 and plug P, working contact of armature 82 and said armature, armature 66 and its resting contact, upper winding of relay 46, and

armature 90 and its resting contact to ground ed battery, in case the receiver is removed during a silent period, or through the generator to battery if the receiver is removed during a ringing period. Upon energizing, relay 46 closes a locking circuit for itself at armature 67 by way of ground at armature 80 and its working contact; and at armatures 66 and 68 disconnects the tip and ring conductors of the plug P from its own upper winding and ground, respectively, and extends them to the windings of the relay 41. Relay 41 is operated and reverses the battery to the calling party, so that a meter or coin col lector can be operated at the calling station, if desired. The calling and called subscribers may now converse with each other as desired,

the talking circuit being outlined by the 80 to the release trunk conductor and guards,

heavy conductors.

At the end of the ensuing conversation, the two subscribers replace their receivers. The replacing of the receiver at the called suhstation A stops battery from flowing over its line and deenergizes relay 41 which prepares at armature 52 a disconnect signal circuit for lamp L.

When the receiver is replaced at substation A, the circuit of the relay 42 is opened and it deenergizes. Upon armature 56 being retracted the circuit of the relay 40 is opened and it deenergizes. Upon armature 39 being retracted, ground is disconnected from the release trunk conductor, whereupon relay 131 of the line switch 0 deenergizes and restores conditions in that switch to normal. At armature 55 the circuit of relay 43 is opened. Relay 43, upon deenergizing, retracts armature 59 which extends ground from armature the cord circuit untilthe operator pulls down the connection, as will be explained hereinafter; and closes at armature 58 a circuit which may be traced from ground, working contact of armature 77 and said armature, resting contact of armature 58 and said armature, armature 52 and its resting contact, and lamp L to grounded battery. Lamp L now glows steadily and indicates to the operator that the parties have hung up.

The operator now pulls the plug P out 'of the jack J, whereupon relays 51 and 213 deenergize. When relay 213 deenergizes it restores conditionsin the switch C to normal. \Vhen relay 51 deenergizes it opens at armature 85 the circuit of relay 50. Relay' 50, upon dceuergizing, opens at. armature 77 the circuit of lamp L and extinguishes it and removes at armature 80 guarding ground from the release trunk conductor. .From this.

it will be seen that all apparatus has been restored to normal condition and is now available for use over again.

Assuming now that the called line is busy when called, as hereinbefore described, line relay 214 and ground are now disconnacted at armatures 216 and 218, respectively, of line switch 0, and if the busy condition is due to this line switch, at the connecting cord, and acircuit may therefore be traced from this grounded conductor, armature 217 and its working contact, sleeve conductors of jack J 2 and plug P, normally closed contact controlled by armature 84, armature 76 and its resting contact, resting contact of armature 71 and said armature, normally closed contact controlled by armature 69, relay 47, armature 73 and its resting contact, and resting contact of armature 88 and said armature, to grounded battery. Relay 47, upon energizing, closes at armature 69 a locking cir cuit for itself by way of ground at resistance 74. Relay 48 was short circuited, but due to the energization of relay 47 as traced above, relay 48 now energizes over part of this circuit by way of the normally resting contact controlled by armature 70, and grounded battery at resistance 92. Relay 48, upon energizing, opens at armature 7 3'the circuit of relay 47: closes at armature a short circuit around its own winding by way of the front contacts of armatures 39 and 69. This short circuit renders the relay 48 slow acting and the same does not release before relay 47 deenergizes. Relay 48 at armature 72 closes a circuit for relay 50; and connects at armature the lead from the busy signalling machine whereby a busy tone is sent back to the calling subscriber to inform him that he cannot obtain the desired connection for the time being. Relay 47, upon deenergizing, opens at armature 69 its locking circuit; at armature 69 opens the short circuit around relay 48 and completes a locking circuit for relay 48 and restores direct ground to the release trunk. Relay 50, upon energizing, performs functions as already described in connection with a completed call, i. e., prepares a disconnect signal circuit; removes relay 49 from across the talking conductors; further opens the waiting tone circuit; and opens the circuits of relays 44, 45 and 102. Relays 44, 45 and 102 deenergize, whereby the operators head set 0 is disconnected, the supervisory lamp L is extinguished, and the switch S is either restored to normal condition or caused to hunt for the stored up calls. If the busy condition is due to an. incoming call relay 49 will energize over the circuit including the back bridge relay of the connected cord circuit but not until relays 47 and 48 have energized due to the sleeves of the plug and jack making contact before the tips and rings. Relay 48 operates to connect the busy tone to the calling subscribers line, etc., as previously ex plained, while nothing happens when relay 49 operates under these conditions.

The calling subscriber upon hearing the busy tone will replace his receiver, wihereupon the connection is released in a manner similar to that previously explained; except relay 48 is released by the falling back of armature 39 of relay 40, and relay 50 is released by the falling back of armature 72 of relay 48. To avoid a possible chance of relay 49 re energizing after the calling subscriberh'angs up and causing the reverting tone to be connected to the operators head set or the ringing current connected to the' busy line erroneously, the circuit of relay 49 includes armature 38 and its associated contact which are always open when the receiver is on the switchhook.

In order to explain the operation a little more in detail, it will be assumed that the subscriber at station A desires to call the subscriber at station A instead of at'station A and that the cord circuit TD is the one seized as previously. The operator upon receiving the order inserts the plug P into the jack J instead of jack J whereupon the ringing current is delivered to the grounded bell at station A over line conductor 212. From this it will be seen that the tip and ring conductors are reversed between multiple jacks J 2 and J this being done preferably at a distributing frame (not shown). The other operations in connection with this call are the same as those already explained for a call from the subscriber at station A to the subscriber at station A Assuming now that the subscriberat station A desires to converse with the subscriber at A on the same line-commonly called a reverting call. The subscriber at station A removes his receiver and is cut throughto the operator in the manner already explained, it being further assumed that the cord circuit TD is used for this purpose. The subscriber orders the desired connection without advice to the operator that it is a reverting connection, whereupon the operator inserts the plug 1 in the jack J without making a busy test. A circuit may now be traced from ground, resting contact of armature 69 and said armature, working contact of armature 39 and said armature, bank contact 25, wiper 22, armature 17 and its working contact, conductor 27, sleeve conductors of jack J and plug P, normally closed contact controlled by armature 84, armature 76 and its resting contact, resting contact of armature 71 and said armature, normally closed contact controlled by armature 69, relay 47 armature 73 and its resting contact, and resting contact of armature 88 and said armature to grounded battery. Relay 47, upon energizing, closes at armature 69 a locking circuit for itself by way of ground at resistance 74. Relay 48 will not now energize over part of this circuit as previously described due to being short circuited as follows, upper terminal of relay 48, front contact 69 of relay 47 front contact 39 of relay 40, wiper 22, front contact 17 of relay 13, sleeve of jack J and plug P, back contact 7 6 of relay 49,-back contact controlled by the armature of relay 48, to the lower terminal of the relay 48. Slightly after the energizing circuit of relay 47 is closed, due to the sleeves of the plug and jack making contact before the tips and rings, a circuit is closed for relay 49 traceable from ground, lower winding of line relay 42, normally closed contact controlled by armature 54, bank contact 26, wiper 23, working contact of armature 18 and said armature, ring of jack J and plug P, armature 79 and its restmg contact, armature 38 and its working contact, relay 49, resting contact of armature 78 and said armature, tip of plug P and jack J, armature 16 and its working contact, wiper 21, bank contact 24, normally closed contact controlled by armature 53, and upper winding of relay 42 to grounded battery.

Relay 49, upon energizing, closes at armature 87 a circuit for relay 95 by way of ground at armature 72; opens at armature 88 the circuit of relay 47; and closes at armature 76 a circuit for relay 51 in series with the switching relay 13 and magnet 15 of the line switch 0. Relay 51 will not, however, energize over this circuit due to being shorted by ground on the release trunk. Relay 47, upon deenergizing, opens at armature 69 its locking circuit and restores direct ground to the release trunk. From this it will be observed that the operator is not released and switched to the next registered call as previously, but is held and given a revertive'tone upon slow acting relay 95 becoming energized. The operator upon hearing the revertive tone pulls the plug P from the jack J, thereby breaking the circuit of relay 49 which deenergizes and opens the circuit of relay 95, whereupon it in turn deenergizes and disconnects said tone. The operator then requests the calling sub- 1scriber to hang up while she rings on the The calling subscriber upon hanging up the receiver deeuergizes the line relay 42, whereupon the line switch C is restored to normal condition and relays 40, 43 and 44 are deenergized, as previously explained. Relay 44, upon deenergizing, opens at armature 60 the holding circuit of relay 102, whereupon said relay deenergizes. If no calls are in waiting switch S rests until a call comes in, but if there is a call in waiting switch S advances to pick it up and cut it in to the op erator as already explained. From this it will be observed that on a reverting call, another call may be cut in to the operator while she is handling the former. She merely receiv'es the order for use later and proceeds with the reverting call connection as will now be explained. The operator reinserts the plug P in the jack J whereupon relay 13 energizes half way, due to the usual mechanical interlocking device; the ringing of the called p'artys bell at station A is started;

and the operator is released from the connection, all in a manner already explained.

When the called subscriber at station A lifts his receiver in response to the ringing of his bell orthe calling subscriber at station A lifts his receiver, thinking the called party has had ample time to answer, the ringing circuit will be opened and the talking circuit closed in a manner already explained. Belay 41 will ener ize, as previously, over the direct current bridge across the subscribers line and in this case will furnish talking battery to both the called and calling subscriber.

Upon completion of the conversation the subscribers will hang up their receivers and relay 41 will deenergize, thus closing at armature 52 the circuit of the supervisory lamp L and notifying the operator of the unoccupied condition of the line. The operator then pulls down the connection and the apparatus is restored to normal condition in a manner already explained.

If for any reason the cut-in control switch S becomes locked up and will not rotate to cut in succeeding calls, an emergency key K is provided, which upon being depressed by the operator, closes a circuit for magnet 104 and shorts out relay 102. When the operator releases the key K the magnet 104 deenergizes and causes the wiper 111 to rotate one step to the next bank contact in which position the switch S is ready for further use.

While the line switches used in connection with this invention are of the rotary type it is to be understood that they may be of the well known Keith plunger type if so desired. In either event the line switches are mounted in standard Strowger automatic switchboards and are thus available for full automatic use at any time without a heavy conversion cost. The outgoing trunks from the line switch banks terminate in cord circuits which are similar to the well known Strowger automatic connectors and may be mounted on bases similar to Strowger automatic repeater bases and then on standard Strowger automatic switchboards. Again it will be seen that a maximum of standard automatic equipment is used to afford an easy and cheap conversion to a full automatic system at any time, thus having a decided advantage over most semi-automatic systems.

Another advantage in the present system lies in the fact that one lamp and one plug only are used in the cord circuits in order that existing manual switchboards may be changed to this system without requiring additional key shelf equipment. This is accomplished by using each cord pair with its associated supervisory lamps for two separate and distinct trunk circuits.

From the above it will be seen that an improved and highly eflicient telephone system I as been provided, in that the service is much faster, more accurate,and the number of calls handled per operator is greatly increased.

Having described my invention, what I consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims. What I claim is: V 4 1. In a telephone exchange system, the

combination with a plurality of operators.

cord circuits, an operators headset and a cord finder and cut-in control switch, of means whereby an idle cord is a-utomaticall seized by an incomin call, means where switch automatically hunts for said seized cord and when found stops hunting and causes said call to be automatically connected to the operators headset, and means for indicating'to the operator to which cord the headset is connected.

2. In a call distributing system, operators cord circuits, automatic switches for connecting calling lines to idle cord circuits, an operators head set, and means including an automatic step by stepswitch having access to said cord circuits for causing cord y said circuits which have been taken for use to be connected to said head set one at a time over talking circuits exclusive of the wipers of said step by step switch. a

3. In a call distributing system, 0 erators cord circuits, automatic switches or connecting calling lines to idle cord circuits, an operators head set, means including an automatic step by step switch for causing cord circuits which have been taken for use to be connected to said head set one at a time, means responsive to the connection of a calling line with an idle cord circuit for operating said switch to locate the cord circuit in use and connect the same to said head set and means preventing further operation 0 said switch until the operator plugs into the called line.

4. In a call distributing system, operators cord circuits, automatic switches for connecting calling lines to idle cord circuits, an operators head set, means including an automatic step by step switch for causing cord circuits which have been taken for use to be connected to said head set one at a time, means responsive to the connection of a calling line with an idle cord circuit for operating said switch to locate the cord circuit in use and connect the same to said head set, means preventing fur-' mamas operators cord circuits, means whereby any one of said lines can be automaticallyconnected to an idle one of said cord circuits -upon a call being originated, a waiting tone 8 machine, means whereby said machine is antomatically connected to said line when same is connected to said idle cord circuit, means for automatically connecting said cord circuit with an operators head set, and means 10 for automatically disconnecting said tone machine to notify the calling subscriber that he is connected with an operator.

6. In a telephone exchange system, a plurality of subscribers lines, a plurality of opvisory lamp, means whereby any one of said lines can be automatically connected to an. idle one of said cord circuits upon a call being originated, means for automatically connecting the cord circuit in use with an operators head set and for flashing the associated lamp to notify her of the call and designate the trunk seized, means for automatically extinguishing said lamp when the operator plugs up the connection; and means for automatically lighting said lamp to a steady glow when the call is terminated and both parties restore their receivers.

7 In a telephone exchange system, a plurality of subscribers lines, an operators cord circuit, an automatic switch for connecting a calling line to said cord circuit, means in said cord circuit responsive when the same is plugged into a called subscribers line for automatically testing said called line for being busy, a circuit for said testing means excluding all talking conductors, a busy tone machine, and means whereby said machine is automatically connected with the calling subscribers line in case the called line is busy.

8. In a telephone system, subscribers lines, an operators cord circuit, an automatic switch for connecting a calling line to said cord circuit, means in said cord circuit responsive when the same is plugged into a called line for testing the called line to ascertain whether or not the calling and called lines are the same, a reverting call tone machine, and means controlled by said testing means for connecting said machine with the operators head set in case the called line is also the calling line.

9. In a telephone system, party lines, an operators cord circuit, means controlled from a calling station for connecting the associated line to said cord circuit, revertive call testing means in said cord circuit automatically responsive when the cord circuit is plugged into the line of the called station, and

signalling the operator in case the calling and called stations are both on the same party line.

10. In a call distributing system, operators cord circuits, automatic switches for connect- 05 ing calling lines to idle cord circuits, an opererators cord circuits each having a supermeans controlledby said testing means for ators head set, means including an automatic step by step switch for causing cord circuits which have been taken for use to be connected to said head set one at a time, means responsive to the connection of a calling line with an idle cord circuit for operating said switch to locate the cord circuit in use and connect the same to said head set, means preventin further operation of said switch until the operator plugs into the called line, means responsive to the act of plugging into the called line for disconnecting said head set from the cord in use and for freeing said switch to enable the same to locate another cord circuit to which a calling line has been connected, and revertive call test means operative to prevent the freeing of said switch and to signal the operator in case the calling and called lines are the same.

11. In a telephone exchange system, the combination with a pluralit-y of operators cord circuits, an operators headset and a cord finder and cut-in control switch, of means whereby an idle cord is automatically seized by an incoming call, means whereby said switch automaticaly hunts for said seized cord and when found stops hunting and causes said call to be automatically extended to the operators headset, and means respon sive to the operator plugging into a .callei'l line for freeing said switch and disconnccting the operators headset.

12. In a call distributing system, operators cord circuits, automatic switches for connecting calling lines to idle cord circuits, an operators headset, means including a hunting and cut-in control switch for finding seized cord circuits and causing same to be connected to said-headset one at a time and means for indicating to the dperator to which cord her headset is connected.

13. In a telephone system, a plu *ality of subscribers lines, a plurality of operators cord circuits, means responsive to the initiation of a call on one of said lines for seizing an idle one of said cord circuits, a waiting tone machine normally connected to said cord circuit, an o perators headset, and automatic means for xtcnding said call to said headset and simultaneously disconnecting said tone machine to notify the calling subscriber that he is connected with the (merator.

connecting said busy machine with said call-' -1ng line, or for connecting said ringing current with said called line, depending upon whether the called line is thecalling line, whether it is busy, or whether is it idle.

' 15. In a call distributing system, operators link circuits, automatic switches for connecting calling'lines to idle link circuits, an

- operators head set, a relay in each link circuit for connecting thelink circuit to said head set, and a common testing switch for successively energizing the relays of link circuits to which calling lines have been connected.

16. In a call distributing system, operators link circuits, automatic switches for connecting calling lines to idle link circuits,

an operators head set, a pair of talking con-.

' said link circuits and arranged to test said link circuits consecutively, and means in each link circuit effective in case the link circuit has a calling line connected to it when it is tested for automatically extending the calling line to said head set.

18. In a call distributing system, subscribers line switches, an automatic testing switch, cordcircuits accessible to said line switches andalso to said testing switch, an

operators circuit, and means in each cord circuit effective only in case the cord circuit hasbeen selected both by said testing switch and by one of said line switches for connecting the cord circuit to said operators circuit.

19. In a call distributing system, subscribers line switches, an automatic testing switch, cord circuits accessible to said line switches and also to said testing-switch, an operators circuit, a relay in each cord circuit for connecting the associated cor-d circuit to said operators circuit, and controlling circuits such that the energization of any relay is made contingent on the selection of 'the associated cord circuit by one of said line switches and also by said testing switch.

20. In a telephone system, a plurality of lines, an operators headset, a device automatically efiective responsive to the initiation of: a call over any line to connect the headset to the line, means effective when the headset is connected to any line to )revent it being connected to other lines, an means effective when the operator completes the call to disconnect the headset provided it is not a reverting call, said last named means being ineffective if the call is a reverting call.

mamas 21. Ina. telephone system, a lurality of lines, an operators headset, a evice automatically effective responsive to-the initiation of a .call over any line to connect the headset to the line, means effective when the headset is connected to any line to prevent its being connected to other lines, means effective when the operator completes the call to disconnect the headset provided it is not a reverting call, and means effective if the call is a reverting call to indicate the fact to the operator,

22. In a telephone system, a plurality of subscribers lines, a plurality of operators cord circuits, an operators headset, an automatic switch for connecting a calling line to an idle cord circuit, a device for finding the cord circuit which has been connected to a calling line, means in each cord circuit effective when the cord has been found to con nect the operators headset to the cord circuit over a circuit exclusive of the device.

23. In a telephone system, subscribers lines, link circuits, means responsive to the initiation of a call over a line for seizing a,

link circuit, an operators headset, a switch common to said link circuits arranged to test said link circuits consecutively, and means in each link circuit controlled by saidswitch to connect the headset to the seized link circuit 1 over a circuit exclusive of the testing switch. 24'. In atelephone system, a plurality of lines, an operators headset and an automatic testing switch common to said lines, and means controlled by the testing switch effective under predetermined conditions for connecting said headset to a line over a circuit exclusive of the testing switch.

25. In a telephone system, a plurality of subscribers lines, a plurality of operators cord circuits, an operators head set, means whereby a calling line may be connected to an idle cord circuit, a device for finding the cord circuit which has been connected to a calling line, means effective responsive to the finding of the cord for connecting the operators head set to the cord circuit and for preventing the further operation of said device, means effective responsive to the completion of: the call by the operator for permit-ting the fur ther operation of said device, and means effective if the call is a reverting call for rendering said last named means ineffective.

26. In a telephone system, subscribers lines, link circuits, means responsive to the initiation of a call over a line for seizing a link circuit, a switch common to said link circuits arranged to test said link circuits successively, circuits effective responsive to the finding of the seized link for preventing further testing operation of said switch, means effective responsive to the completion of the call by the operator for permitting the further testing operation of said switch, and

means effective if the call is a reverting call circuit controlled by said device for connect- 10 for rendering said last named means inefing the operators head set to the connected feetive. cord circuit over a circuit exclusive of the de- 27. 'In a telephone system, a plurality of vice, and means for indicating to the operator 6 lines, a plurality of operators cord circuits, the cord circuit connected with. i

an operators head set, means whereby a line In witness whereof, I hereunto subscribe 15 may be connected to an idle cord circuit, a. demy name this 21stday of April, A. D. 1924.

vice for finding the cord circuit which has been connected to a line, means in each cord BERNARD D. VVILLIS. 

